South Korea and Taiwan unveiled new monuments dedicated to tens of thousands of Asian women forced to work in Japanese military brothels during World War II.
In Seoul, ceremonies marked the country's first Memorial Day for Japanese Forces' Comfort Victims on Tuesday.
The legacy of the estimated 200,000 girls and young women from South Korea, China, the Philippines, and Japan who were kidnapped and forced into sexual slavery by the Imperial Japanese Army is a flashpoint in diplomatic relations between Japan and its neighbours.
"My hope is that this issue will not lead to a diplomatic dispute between South Korea and Japan. I also do not think that this will be solved by a bilateral diplomatic solution," South Korean President Moon Jae-in said on Tuesday.
Moon said the issue involves the "entire world" and the human rights of all women. He pledged South Korea's government would keep the plight of "comfort women" known through commemorative projects.
In South Korea, there are 37 survivors of wartime sexual slavery, mostly in their late 80s or early 90s.
Tuesday's commemorations were likely to cause anger in Japan, where demonstrations have previously taken place over existing monuments dedicated to comfort women, including one in front of the Japanese embassy in Seoul.
Tokyo also protested the move last year to make August 14 a day of official remembrance. The date was chosen because on August 14, 1991, Kim Hak-sun, a South Korean victim, became the first woman to speak publicly about her ordeal.
'Final and irreversible'
Japan has repeatedly said the issue was resolved by a 2015 dealstruck with the previous South Korean administration, which provided an official apology and 1bn yen ($9.03m) to establish a foundation to help surviving women.
The agreement was said to be a "final and irreversible" conclusion to the issue.
More than 50 activists joined a sit-in outside Japan's de facto embassy in Taiwan's capital, Taipei, demanding a formal apology and monetary compensation for Taiwanese women forced to work in wartime brothels.
Protesters wore black T-shirts and white masks and shouted "the Japanese government must apologise", AFP news agency reported. A bronze statue to victims was also unveiled in Tainan city, according to the United Daily News.
Rallies were also expected in the Philippine capital, Manila.
